WASHINGTON- - Former U.S. Attorney General William Barr on Sunday defended Special Counsel Jack Smith's 37-count indictment against Donald Trump on Sunday, saying if the allegations the former president willfully retained hundreds of highly classified documents are proven true, then "he's toast." "I was shocked by the degree of sensitivity of these documents and how many there were, ... and I think the counts under the Espionage Act that he willfully retained those documents are solid counts," Barr, who served under Trump, told "Fox News Sunday." "If even half of it is true, then he's toast." The comments from Barr, who was Trump's attorney general from February of 2019 through December of 2020, are notable and were made at a time when many other prominent Republicans have been hesitant to criticize the former president and current Republican front-runner in the 2024 White House race. Trump responded to Barr's comments with criticism and insults. Describing Barr as a "lazy" and "weak" attorney general, Trump on his social media platform Truth Social said he only made the comments because he was disgruntled and that they were misinformation. "Turn off Fox News when that "Gutless Pig" is on," Trump said. The former president is due to appear in a federal courthouse in Miami on Tuesday to make his initial appearance on the charges, which include the willful retention of highly sensitive national defense records under the Espionage Act, obstruction of justice, making false statements, conspiracy and concealment. Trump told Politico on Saturday that he would continue his presidential campaign, even if he were convicted in the case, saying "I'll never leave." He plans to make remarks at 8:15 p.m. on Tuesday (0015 GMT on Wednesday) at his Bedminster, New York, golf club, his presidential campaign said. Meanwhile, hundreds of pro-Trump supporters drove in a caravan from Miami to Palm Beach on Sunday to show their support for the former president, as has been done on several previous occasions since he left office. Cars decked out with American flags and pro-Trump slogans on placards made the 80-mile (130-km) trip, honking most of the way and meeting at a Palm Beach grocery store parking lot for a rally. Of the 37 counts against Trump, 31 of them relate to secret and top secret classified documents that he kept after leaving the White House in early 2021. The indictment alleges that Trump stored the documents in a haphazard manner at his home in Palm Beach, Florida, refused to give them back to the government, and tried to hide them from the FBI and even his own attorney after a grand jury issued him a subpoena demanding that he turn over all records bearing classified markings. His attorney Alina Habba, who is not representing him in the case, told "Fox News Sunday" that Trump is innocent of the charges and plans to vigorously defend himself in the case. In the past, Barr has been a fierce defender of Trump, going so far as to appoint his own special counsel to probe whether the FBI improperly opened an investigation into Trump's 2016 presidential campaign over possible ties to Russia based on flimsy evidence. But towards the end of his tenure, Barr's views on Trump soured after the former president tried to pressure the Justice Department to launch bogus voter fraud investigations, in a failed bid to overturn the results of the 2020 presidential election. Not 'PERSONAL Documents' Trump has previously defended his retention of classified records, claiming without evidence he declassified them while in office - a defense that his allies have also repeated. "I go on the president's word that he said he did," U.S. House of Representatives Judiciary Committee Chairman Jim Jordan told CNN's "State of the Union" program on Sunday when asked if he had any evidence to back up Trump's claim. In previous litigation related to the FBI's search of his Florida home, however, Trump's lawyers repeatedly declined to make that argument in their court filings, and the indictment also contains evidence that Trump knew he had retained records that remained highly classified. "As president, I could have declassified it," the indictment quotes Trump as saying about one military document he allegedly displayed during a meeting at his New Jersey golf club in July of 2021. "Now I can't, you know, because this is still a secret." Trump and his allies have also separately tried to argue that the records at the heart of the case are personal in nature and covered by the Presidential Records Act. "He has every right to have classified documents that he declassifies under the Presidential Records Act," Habba told Fox News Sunday. But Barr said the claim that the documents were Trump's personal records is "facially ridiculous." The records referenced in the indictment are "official records" prepared by government intelligence agencies, he said, and therefore they are the property of the U.S. government. "Battle plans for an attack on another country or Defense Department documents about our capabilities are in no universe Donald J. Trump's personal documents," he said.